Benzodithiophene based copolymer containing thieno [3,4-B] thiophene units and preparing method and applications thereof

ABSTRACT

The present invention relates to a benzodithiophene based copolymer containing thieno[3,4-b]thiophene units and a preparing method and applications thereof. The polymer has a structural formula (I), wherein R 1  and R 2  are respectively selected from H, and alkyl groups of C 1  to C 16 ; R 3  and R 4  are respectively selected from H, alkyl groups of C 1  to C 16 , alkoxy groups of C 1  to C 16 , or thiophene groups substituted by alkyl groups of C 1  to C 16 ; R 5  is selected from alkyl groups of C 1  to C 16 ; n is a natural number from 7 to 80. Applications of the benzodithiophene based copolymer containing thieno[3,4-b]thiophene units in polymer solar cells, polymer organic light-emission, polymer organic field effect transistors, polymer organic optical storage, polymer organic nonlinear materials or polymer organic laser are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase filing under 35 U.S.C. §371 ofPCT/CN2012/085677 filed on Nov. 30, 2012, the entire contents of whichis hereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to the field of benzodithiophene basedcopolymer, more particularly relates to a benzodithiophene basedcopolymer containing thieno[3,4-b]thiophene units and preparing methodand applications thereof.

BACKGROUND OF THE INVENTION

The organic solar cell, as a potential renewable energy, has attractedwide attention, which has some incomparable advantages better thaninorganic solar cell, such as low cost, simple manufacturing process,light-weight, and it can be made flexibly in great area and so on. Overthe past decade, the performance of the organic solar cell has improved,and the energy conversion efficiency is close to 10%.

The energy conversion efficiency of the organic solar cell has improvedgreatly; however, so far, the energy conversion efficiency of theorganic solar cell is much lower than that of the inorganic solar cell.Therefore, in order to make the organic solar cell be implementedcommercially, it is significant to develop a new organic semiconductormaterial for improving the efficiency of the organic solar cell.

In recent years, due to the development of the conjugated polymers inthe design and the fabrication process of the device, the efficiency ofthe polymer solar cell has remarkably improved. In future, one challengeof the polymer solar cell is to synthesize a new P-type-conjugatedpolymer, which needs to have features of: (a) good solubility, whichfacilitates for processing and performing industrial production; (b)broad and strong absorption to the entire solar spectrum; (c) highcarrier mobility, which facilitates for carrier transport. Researcheshave focused on broadening the light absorption range of the polymermaterials and making the light absorption maximally cover the entirespectrum of solar light. Choosing an appropriate monomer in thesemiconductor polymer backbone can broaden the light absorption range toinfrared and near infrared. However, it fails to find such appropriatemonomer in the prior art.

SUMMARY OF THE INVENTION

The present invention is directed to provide a benzodithiophene basedcopolymer containing thieno[3,4-b]thiophene units, which iscopolymerized by benzodithiophene monomers and thieno[3,4-b]thiophenemonomers, the absorption band-edge shifts towards the infrared and nearinfrared region for better matching the emission spectrum of thesunlight.

The present invention is also directed to provide a method for preparinga benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits.

The present invention is also directed to uses of benzodithiophene basedcopolymer containing thieno[3,4-b]thiophene units in polymer solarcells, organic electroluminescent devices, organic field effecttransistors, organic optical storage, organic non-linear devices, ororganic laser.

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits has a structural formula:

wherein R₁ and R₂ are selected from the group consisting of H, and C₁ toC₁₆ alkyl, respectively; R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, and thienylsubstituted by C₁ to C₁₆ alkyl, respectively; R₅ is C₁ to C₁₆ alkyl; nis a natural number from 7 to 80.

In the benzodithiophene based copolymer, the alkyl is a linear alkyl orbranched alkyl; the alkoxy is a linear alkoxy or branched alkoxy.

In the benzodithiophene based copolymer, n is a natural number from 8 to60.

In the benzodithiophene based copolymer, R₁ is the same as R₂, and/or R₃is the same as R₄.

In the benzodithiophene based copolymer, R₁, R₂, R₃, R₄ and R₅ areselected from a combination of: R₁ and R₂ are H, R₃ and R₄ are methyl,R₅ is n-butyl; or R₁, R₂, R₃, and R₄ are H, R₅ is methyl; or R₁ isethyl, R₂ is pentyl, R₃ is H, R₄ is 3-methyl thienyl, R₅ is 2-methylbutyl; or R₁ and R₂ are identical propyl, R₃ is 12 alkyl, R₄ is ethoxyl,R₅ is 2,4-dimethyl-3-ethyl heptyl; or R₁ is butyl, R₂ is 12 alkyl, R₃ is14 alkoxy, R₄ is octyl, R₅ is 2,2,4-trimethyl pentyl; or R₁ and R₂ areidentical H, R₃ is octoxy, R₄ is H, R₅ is 16 alkyl; or R₁ is hexyl, R₂is H, R₃ is 2-methyl thienyl, R₄ is H, R₅ is octyl; or R₁ is 16 alkyl,R₂ is H, R₃ is methoxyl, R₄ is H, R₅ is methyl; or R₁ is H, R₂ ismethyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical methyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂are identical H, R₃ is hexyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ is methyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ and R₄ are identical H, R₅ is butyl.

A method for preparing a benzodithiophene based copolymer containingthieno[3,4-b]thiophene units includes the steps of:

adding M1 and M2 to a solvent in an oxygen-free environment;

performing a refluxing reaction in the presence of catalyst; thereaction formula is as follows:

wherein R₁ and R₂ are selected from the group consisting of H, and C₁ toC₁₆ alkyl, respectively; R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, and thienylsubstituted by C₁ to C₁₆ alkyl, respectively; R₅ is C₁ to C₁₆ alkyl; nis a natural number from 7 to 80; wherein a molar ratio between M1 andM2 is 1:1 to 1.5:1; the solvent is at least one selected from the groupconsisting of toluene, tetrahydrofuran, benzene, andN,N-dimethylformamide; the catalyst is organic palladium or a mixture oforganic palladium and organic phosphine ligand, a molar amount of thecatalyst is 0.01% to 5% of the molar amount of the M2; the organicpalladium is Pd₂(dba)₃, Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂, a molar ratio betweenthe organic palladium and the organic phosphine ligand in the mixture is1:2 to 1:20; the organic phosphine ligand is P(o-Tol)₃ ortricyclohexylphosphine; the reaction is performed at a temperatureranging from 60° C. to 120° C. for 12 to 72 hours.

In the method, M1 is synthesized by the steps of:

S1, dissolving a compound A with a proper amount of dichloromethane toform a solution, under a nitrogen atmosphere, adding the solutiondropwise to anhydrous dichloromethane containing1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine by a syringe;wherein a molar ratio of the compound A, the1,3-dicyclohexylcarbodiimide, and the 4-dimethylaminopyridine is 3:3:1,the reaction is performed for 8 to 24 hours to obtain a compound B, thereaction formula is as follows:

S2, adding the compound B and the compound C to a solvent according amolar ratio of 1:1, the solvent is ethanol or propanol; heating to 78°C. to 100° C. to perform a refluxing reaction, then adding a reducingagent, and reacting for additional 10 minutes to obtain a compound D;the reducing agent is potassium hydroxide or sodium hydroxide, a molarratio between the reducing agent and the compound B is 5:1; the reactionis performed for additional 10 minutes to obtain the compound D afterthe reaction solution becomes dark green;

S3, under a nitrogen atmosphere, dissolving the compound D to anhydroustetrahydrofuran and cooling to −78° C.; adding an n-hexane solutioncontaining n-butyllithium slowly, a molar ratio between then-butyllithium (n-BuLi) and the compound D is 1:2.5; reacting understirring at a temperature of −78° C. for 2 hours; then adding trimethyltin chloride, a molar ratio between the trimethyl tin chloride (Me₃SnLi)and the compound D is 2.5:1; incubating for 0.5 hours and then returningto room temperature; and reacting for additional 24 hours to obtain thecompound M1; the reaction formula is as follows:

In the method, the alkyl is a linear alkyl or branched alkyl; the alkoxyis a linear alkoxy or branched alkoxy, n is a natural number from 8 to60.

In the method, R₁ is the same as R₂, and/or R₃ is the same as R₄; or R₁,R₂, R₃, R₄ and R₅ are selected from a combination of: R₁ and R₂ are H,R₃ and R₄ are methyl, R₅ is n-butyl; or R₁, R₂, R₃, and R₄ are H, R₅ ismethyl; or R₁ is ethyl, R₂ is pentyl, R₃ is H, R₄ is 3-methyl thienyl,R₅ is 2-methyl butyl; or R₁ and R₂ are identical propyl, R₃ is 12 alkyl,R₄ is ethoxyl, R₅ is 2,4-dimethyl-3-ethyl heptyl; or R₁ is butyl, R₂ is12 alkyl, R₃ is 14 alkoxy, R₄ is octyl, R₅ is 2,2,4-trimethyl pentyl; orR₁ and R₂ are identical H, R₃ is octoxy, R₄ is H, R₅ is 16 alkyl; or R₁is hexyl, R₂ is H, R₃ is 2-methyl thienyl, R₄ is H, R₅ is octyl; or R₁is 16 alkyl, R₂ is H, R₃ is methoxyl, R₄ is H, R₅ is methyl; or R₁ is H,R₂ is methyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical methyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂are identical H, R₃ is hexyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ is methyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ and R₄ are identical H, R₅ is butyl.

Uses of the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units according to any one in polymer solarcells, polymer organic electroluminescent devices, polymer organic fieldeffect transistors, polymer organic optical storage, polymer organicnon-linear devices, or polymer organic laser.

An appropriate monomer is selected for the semiconductor polymerbackbone, which is beneficial to broaden the light absorption range toinfrared and near infrared. In the benzodithiophene based copolymercontaining thieno[3,4-b]thiophene units, an electron-rich donor and anelectron-deficient acceptor unit are introduced to the polymer backbone;the energy gap of the conjugated polymer is reduced due to the“push-pull electrons” interaction of the donor and acceptor, thus theabsorption band shifts towards low energy band of the infrared and nearinfrared. In the benzodithiophene derivatives, two thiophenes areconnected in one plane by fused ring, its planarity and rigidity areenhanced, the copolymer has high optical, thermal and environmentalstabilities. The central benzene ring decreases the electron-rich numberof the thiophene rings located on two sides, thus the copolymer has muchlower highest occupied orbital (HOMO) level. The π-π stackings betweenthe π-bonds have much higher carrier mobility due to the existence ofthe extended conjugated π-bonds system. Therefore, the copolymer can bewidely applied in the fields of organic electronics and so on; it canalso be used to develop organic solar cell with low cost and highefficiency.

The main advantages of the present disclosure also include:

1. The synthetic routes of the benzodithiophene monomer M1 andthieno[3,4-b]thiophene monomer M2 are simple and mature, theintroduction of the alkyl can improve the solubility and molecularweight of the product, thus the obtained polymer or oligomer can bespin-coated;

2. The benzodithiophene monomer M1 is a kind of excellent donor materialand the thieno[3,4-b]thiophene monomer M2 is a kind of excellentreceptor material, the polymer composed of the monomers M1 and M2 canform a donor-acceptor structure, on one hand, the stability of thematerial is improved, on the other hand, the band-gap of the material isreduced, thus the solar absorption range is broadened, and thephotoelectric conversion efficiency is improved;

3. Stille coupling reaction is a very mature polymerization, it has highyield and mild conditions, and it is easy to control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structure view of the organic solar cell accordingto example 9;

FIG. 2 is a schematic structure view of the organic electroluminescentdevice according to example 10; and

FIG. 3 is a schematic structure view of the organic field effecttransistor according to example 11.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Some preferred embodiments of the present disclosure will be describedin detail referring to the drawings.

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits is provided. First of all, a cyclopentadienyl ring of an innerketone structure is fused on the benzene ring, which can enhance theplanarity and conjugation of the fused ring system. Therefore, thecarrier mobility of the polymer is enhanced. Meanwhile, thiophene ringsare introduced to both sides of the cyclopentadienone, and the alkylsare introduced to 3 and 4 sites of the thiophene to increase itssolubility. The benzothiophene monomer is copolymerized withthieno[3,4-b]thiophene monomer of the strong receptor, and a “weakdonor-strong acceptor” copolymer molecule is formed, which helps toreduce the optical energy gap, expand the light absorption range of thematerial, and improve sunlight utilization of the material.

In an embodiment, the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units has a structural formula:

wherein R₁ and R₂ are identical or different, R₁ and R₂ are H or C₁ toC₁₆ alkyl, including linear alkyl or branched alkyl; or R₁ and R₂ arecycloalkyl. R₃ and R₄ are identical or different, R₃ and R₄ are H, C₁ toC₁₆ alkyl, C₁ to C₁₆ alkoxy, or thienyl substituted by C₁ to C₁₆ alkyl;R₅ is C₁ to C₁₆ linear alkyl or branched alkyl; n is a natural numberfrom 8 to 60.

In another embodiment, a method for preparing a benzodithiophene basedcopolymer containing thieno[3,4-b]thiophene units is provided, thereaction formula is as follows:

The method includes the steps of:

M1 and M2 are added to a solvent in an oxygen-free environment;

a refluxing reaction is performed in the presence of catalyst; and thebenzodithiophene based copolymer containing thieno[3,4-b]thiophene unitsis obtained. A molar ratio between M1 and M2 is 1:1 to 1.5:1; in anembodiment, the molar ratio between M1 and M2 is 1.12:1, 1.2:1, 1.3:1,1.35:1, 1.4:1 or 1.48:1 and so on.

In an embodiment, M2 is4,6-dibromo-2-(1-octanone)-thieno[3,4-b]thiophene or4,6-dibromo-2-(1-(2-ethylhexan-1-one))-thieno[3,4-b]thiophene and thelike, which is depended on the R₅, the preparation is referred to themethod in the prior art.

Preferably, M1 and M2 are added to the solvent in an oxygen-freeenvironment, and the refluxing reaction is performed in the presence ofthe catalyst. In an embodiment, the reaction is performed under anitrogen atmosphere or under an inert gas atmosphere, such as nitrogen.

R₁ and R₂ are selected from H or C₁ to C₁₆ alkyl, respectively. In anembodiment, R₁ and R₂ are selected from H or C₁ to C₁₆ linear alkyl orbranched alkyl, respectively, such as hydrogen, methyl, ethyl, propyl,n-pentyl, 2-methyl butyl, isobutyl, 4-methyl heptyl and the like. Therepeating structural units of the benzodithiophene based copolymer areincluded in the parenthesis, the symbol of “*” represents aconstitutional repeating unit connecting to the next unit.

R₃ and R₄ are selected from H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, orthienyl substituted by C₁ to C₁₆ alkyl, respectively. In an embodiment,R₃ and R₄ are selected from H, C₁ to C₁₆ linear alkyl or branched alkyl,C₁ to C₁₆ linear alkoxyl or branched alkoxyl, or thienyl substituted byC₁ to C₁₆ linear alkyl or thienyl substituted by C₁ to C₁₆ branchedalkyl, respectively; such as hydrogen, n-pentyl, isobutyl, 4-methylheptyl, 2-methyl 4-ethyl nonyl, iso-propoxy, n-pentyloxy, thienyl,2-methyl thienyl, 3-ethylene-thienyl, etc.

R₅ is C₁ to C₁₆ alkyl. In an embodiment, R₅ is C₁ to C₁₆ linear alkyl orbranched alkyl, such as methyl, ethyl, n-pentyl, isobutyl, 4-methylheptyl, 2-methyl 4-ethyl nonyl, and the like.

n is a natural number from 7 to 80. In an embodiment, n is a naturalnumber from 8 to 60. Alternatively, n is a natural number from 10 to 50,or n is a natural number from 15 to 45. In an embodiment, n is 18, 20,24, 25, 26, 27, 29, 31, 33, 35, 36, 38, 42 and the like. Generally, theratio of reactants and/or reaction time are depended on the subsequentproduct application, accordingly, the degree of polymerization isadjusted.

The solvent is at least one selected from the group consisting oftoluene, tetrahydrofuran, benzene, and N,N-dimethylformamide. Thesolvent is sufficient, which generally means that the solvent cancompletely dissolve the solute, or the solvent is enough for thereaction etc. In an embodiment, the solvent is toluene, tetrahydrofuran,benzene, and N,N-dimethylformamide, alternatively, the solvent is amixed solvent of toluene and tetrahydrofuran with a molar ratio form 1:1to 1.5:1; alternatively, the solvent is a mixed solvent of toluene,tetrahydrofuran and benzene with a molar ratio from 1:1:1 to 2:1:2 etal. Preferably, the solvent is a mixed solvent of toluene,tetrahydrofuran, benzene, and N,N-dimethylformamide with a molar ratioof 1:1:1:1 or a mixed solvent of toluene and benzene with a molar ratioof 1:1. Usually, the reaction is performed in an oxygen-freeenvironment; in an embodiment, the reaction is performed under nitrogenenvironment. Alternatively, the reaction is performed via filling withnitrogen or inert gas.

The catalyst is organic palladium or a mixture of organic palladium andorganic phosphine ligand, the molar amount of the catalyst is 0.01%/˜5%of the molar amount of the M2. The organic palladium is Pd₂(dba)₃,Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂, a molar ratio between the organic palladiumand the organic phosphine ligand in the mixture is 1:2 to 1:20. In anembodiment, the catalyst is organic palladium or a mixture of organicpalladium and organic phosphine ligand, the molar amount of the catalystis 0.01%˜5% of the molar amount of the M2. The organic phosphine ligandis P(o-Tol)₃ or tricyclohexylphosphine or a combination thereof. In anembodiment, the molar amount of the catalyst is 0.1%, 0.12%, 0.2%, 0.3%,0.45%, 0.67%, 0.8%, 1.1% or 2.3% of the molar amount of the M2. Theorganic palladium is Pd₂(dba)₃, Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂. A molar ratiobetween the organic palladium and organic phosphine ligand in themixture is 1:2 to 1:20. In an embodiment, a molar ratio between theorganic palladium and organic phosphine ligand in the mixture is 1:2.5,1:3, 1:5, 1:6.8, 1:8, 1:9, 1:11, 1:14, 1:18 or 1:19.5. In an embodiment,a molar ratio between the Pd₂(dba)₃ and P(o-Tol)₃ is 1:3 or 1:2.

The reaction is performed at a temperature ranging from 60° C. to 120°C. for 12 to 72 hours. In an embodiment, the reaction temperature is 61°C., 65° C., 72° C., 78° C., 80.5° C., 87° C., 91° C., 105° C. or 119° C.The reaction time is 12.5 hours, 14 hours, 22 hours, 24 hours, 28 hours,37 hours, 44 hours, 49 hours, 56 hours, 64 hours or 71 hours.Preferably, the reaction temperature and reaction time are mutualdepended to each other, when the reaction temperature is high, then thereaction time is relatively reduced, which can be adjusted according toactual situation.

In an embodiment, M1 is synthesized by the steps of:

Step one, the compound A is dissolved with an appropriate amount ofdichloromethane to form a solution, under a nitrogen atmosphere, thesolution is added to anhydrous dichloromethane containing DCC(1,3-dicyclohexylcarbodiimide) and DMPA (4-dimethylaminopyridine)dropwise by a syringe, wherein a molar ratio of the compound A, DDC andDMAP is 3:3:1, the reaction is performed over night to obtain theproduct of the compound B, the reaction formula is as follows:

In an embodiment, the reaction is performed for 8 to 24 hours. In anembodiment, the molar ratio of A, DCC and DMAP is 3.5:3:1, 3:3:1.5, or2:2.2:1. Alternatively, the reaction is performed for 8.5 hours, 9hours, 11 hours, 15.5 hours, 18 hours or 22 hours, etc.

Step two: the compound B and the compound C are added to the solventwith a molar ratio of 1.0:1.0, then heated to 78° C. to 100° C. toperform a refluxing reaction, and an appropriate amount of potassiumhydroxide/sodium hydroxide is added, wherein a molar ratio of thepotassium hydroxide/sodium hydroxide and the compound B is 5:1. Thereaction is performed for additional 8 to 12 minutes after the reactionsolution becomes dark green, preferably for 10 minutes, the product isobtained, i.e. the compound D. The solvent is ethanol, propanol, etc.The reaction formula is as follows:

In an embodiment, a molar ratio of the compound B and the compound C is1:1, the compound B and the compound C are added to ethanol, propanol ora mixture thereof. In an embodiment, a molar ratio of the ethanol andthe propanol is 1:1, 2:1, 1:2 etc. The solution is heated to 78° C. to100° C. for refluxing. In an embodiment, the solution is uniformlyheated to 80° C., 85° C., 90° C., 91° C., 96° C. or 99° C. for refluxingreaction. A reducing agent is added prior to heating, during heating orwhen the temperature is more than 78° C. Preferably, the reducing agentis added when the temperature is more than 78° C. In an embodiment, thereducing agent is sodium hydroxide, the molar ratio of the sodiumhydroxide and the compound B is 5:1.

Step three: under a nitrogen atmosphere, the anhydrous tetrahydrofuransolution of the compound D is cooled to −78° C., thenn-BuLi(n-butyllithium) solution is slowly added, a molar ratio of then-BuLi and the compound D is 1:2.5. The reaction is performed for 2hours at −78° C. in stirring, then the trimethyl tin chloride reagent isadded, a molar ratio of Me₃SnCl and D is 2.5:1, the reaction solutionreturns to room temperature after incubating for 0.5 hours, and thenreaction is performed for additional 24 hours, the product is obtained,i.e. the compound M1; the reaction formula is as follows:

In an embodiment, R₁ and R₂ are identical, and R₃ and R₄ are identical.Alternatively, R₁ and R₂ are identical, R₃ and R₄ are different.Alternatively, R₁ and R₂ are different, R₃ and R₄ are identical.Alternatively, R₁, R₂, R₃, R₄, and R₅ are selected a combination fromthe group consisting: R₁ and R₂ are H, R₃ and R₄ are methyl, R₅ isn-butyl; alternatively, R₁, R₂, R₃, R₄ are H, R₅ is methyl;alternatively, R₁ is ethyl, R₂ is pentyl, R₃ is H, R₄ is 3-methylthienyl, R₅ is 2-methyl butyl; alternatively, R₁ and R₂ are identicalpropyl, R₃ is 12 alkyl; R₄ is ethoxyl; R₅ is 2,4-dimethyl-3-ethylheptyl; alternatively, R₁ is butyl, R₂ is 12 alkyl, R₃ is 14 alkoxy, R₄is octyl, R₅ is 2,2,4-trimethyl pentyl; alternatively, R₁ and R₂ areidentical H, R₃ is octoxy, R₄ is H, R₅ is 16 alkyl; alternatively, R₁ ishexyl, R₂ is H, R₃ is 2-methyl thienyl, R₄ is H, R₅ is octyl;alternatively, R₁ is 16 alkyl, R₂ is H; R₃ is methoxyl; R₄ is H, R₅ ismethyl; alternatively, R₁ is H, R₂ is methyl, R₃ is 16 alkoxy, R₄ is H,R₅ is butyl; alternatively, R₁ and R₂ are identical methyl, R₃ is 16alkoxy, R₄ is H, R₅ is butyl; alternatively, R₁ and R₂ are identical H,R₃ is hexyl; R₄ is H, R₅ is butyl; alternatively, R₁ and R₂ areidentical H, R₃ is methyl, R₄ is H, R₅ is butyl; alternatively, R₁ andR₂ are identical H, R₃ and R₄ are identical H, R₅ is butyl.

In an embodiment, the benzodithiophene based copolymer containing thieno[3,4-b]thiophene units has the following structural formula:

wherein R₁ and R₂ are identical or different, and R₁ and R₂ are selectedfrom the group consisting of H, and C₁ to C₁₆ alkyl, respectively; R₃and R₄ are identical or different, R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, or thienylsubstituted by C₁ to C₁₆ alkyl, respectively; R₅ is C₁ to C₁₆ linearalkyl or branched alkyl; n is a natural number from 8 to 60.

In an embodiment, R₁ and R₂ are selected from the group consisting of Hand C₁ to C₁₆ alkyl, respectively. In an embodiment, R₁ and R₂ areselected from the group consisting of H and C₁ to C₁₆ linear or branchedalkyl, respectively; such as hydrogen, methyl, ethyl, propyl, n-pentyl,2-methylbutyl, isobutyl, 4-methyl heptyl, decyl, linear or branched 12alky, linear or branched 16 alkyl and the like. The repeating structuralunits of the benzodithiophene based copolymer are included in theparenthesis, the symbol * represents a constitutional repeating unitconnecting to the next unit.

R₃ and R₄ are selected from the group consisting of H, C₁ to C₁₆ alkyl,C₁ to C₁₆ alkoxy, and thienyl substituted by C₁ to C₁₆ alkyl,respectively. In an embodiment, R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ linear alkyl or branched alkyl, C₁ to C₁₆linear alkoxy or branched alkoxy, and thienyl substituted by C₁ to C₁₆linear alkyl or branched alkyl, respectively; such hydrogen, n-pentyl,isobutyl, 4-methyl heptyl, 2-methyl 4-ethyl nonyl, iso-propoxy,n-pentyloxy, thienyl, 2-methylthienyl, 3-ethylene-thienyl, etc.

R₅ is C₁ to C₁₆ alkyl. In an embodiment, R₅ is C₁ to C₁₆ linear orbranched alkyl, such as methyl, ethyl, n-pentyl, isobutyl, 4-methylheptyl, 2-methyl 4-ethyl nonyl, and the like.

In an embodiment, the alkyl in the aforementioned embodiments ispartially or fully fluorinated.

n is a natural number from 7 to 80. In an embodiment, n is a naturalnumber from 8 to 60. Alternatively, n is a natural number from 10 to 50,or n is a natural number from 15 to 45. In an embodiment, n is 18, 20,24, 25, 26, 27, 29, 31, 33, 35, 36, 38, 42 and the like. Generally, theratio of reactants and/or the reaction time are depended on theapplications of the subsequent products; accordingly, the degree ofpolymerization is adjusted.

In the aforementioned embodiments, R₁ and R₂ are identical, and R₃ andR₄ are identical. Alternatively, R₁ and R₂ are identical, R₃ and R₄ aredifferent. Alternatively, R₁ and R₂ are different, R₃ and R₄ areidentical.

In an embodiment, in the benzodithiophene based copolymer, R₁ and R₂ areH, R₃ and R₄ are methyl, R₄ is methyl, R₅ is n-butyl. Alternatively, R₁,R₂, R₃, and R₄ are H, R₅ is methyl.

In an embodiment, the structural formula is as follows:

wherein R₁ is ethyl, R₂ is pentyl, R₃ is H, R₄ is 3-methyl thienyl, R₅is 2-methyl butyl. In an embodiment, R₂ is n-pentyl or isopentyl, i.e.linear alkyl and branched alkyl are suitable (similarly hereinafter). Inan embodiment, the structural formula is as follows:

wherein R₁ and R₂ are identical propyl, R₃ is 12 alkyl, R₄ is ethoxyl,R₅ is 2,4-dimethyl-3-ethyl heptyl.

In an embodiment, the structural formula is as follows:

wherein R₁ is butyl, R₂ is 12 alkyl, R₃ is 14 alkoxy, R₄ is octyl, R₅ is2,2,4 trimethyl pentyl.

For a better understanding of the present disclosure, the technicalsolution of the present disclosure is further illustrated by thespecific examples.

Example 1

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ and R₂ are identical H, R₃ is octoxy, R₄ is H, R₅ is 16alkyl, n=60.

The preparation of the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units includes the steps of:

Step one, the preparation of 1,3-bis(2-thiophene) acetone was describedbelow.

First, 7.6 g (36.8 mmol) of DCC and 1.23 g (10 mmol) of DMAP weredissolved in 70 mL of dichloromethane via anhydrous treatment to form areaction solution; under a nitrogen atmosphere, 70 mL of dichloromethanesolution containing 5 g (35.2 mmol) of 2-thiophene acetic acid was addeddropwise to the reaction solution, the reaction was performed overnight.After the reaction was finished, the reaction solution was filtered,recrystallized with n-hexane for twice, and purified by columnchromatography to obtain a product.

MALDI-TOF-MS (Matrix-Assisted Laser Desorption/Ionization Time of FlightMass Spectrometry) mass-to-charge ratio (m/z) was 222.3 (M⁺).

For example, the dichloromethane was treated with calcium chloride orpotassium carbonate to obtain anhydrous dichloromethane, then stirredand kept overnight, and distilled.

Step two, the preparation of2,7-dioctyloxybenzo[1,2-b:4,3-b′]dithiophene-4,5-diketone was describedbelow:

25.4 g (i.e. 60 mmol) of 4,4′-bis(2-octyloxy)thiophene was added to 400mL of dry 1,2-dichloroethane, i.e. 25.4 g (i.e. 60 mmol) of4,4′-bis(2-octyloxy)thiophene was added to a reaction flask having 400mL of 1,2-dichloroethane or 400 mL of 1,2-dichloroethane via drytreatment, similarly hereinafter; then 3 mL (i.e. 34.5 mmol) of oxalylchloride was added to the reaction flask for three times within 5 days,and the refluxing reaction was performed for 15 days under an argonatmosphere. After the reaction was finished, the reaction solution wascooled to room temperature; and frozen overnight in the refrigerator;then filtered to obtain a red solid, and the red solid was washed withn-hexane and ethanol successively to obtain a product.

MALDI-TOF-MS (m/z) was 477.0 (M⁺)

In an embodiment, 1 mL of oxalyl chloride was added on the first day, 1mL of oxalyl chloride was added on the third day, 1 mL of oxalylchloride was added on the fifth day. Alternatively, 1 mL of oxalylchloride was added on the first day, 0.5 mL of oxalyl chloride was addedon the second day, 1.5 mL of oxalyl chloride was added on the fifth day.Alternatively, 0.5 mL of oxalyl chloride was added on the first day, 1mL of oxalyl chloride was added on the third day, 1.5 mL of oxalylchloride was added on the fifth day.

Step three, the preparation of2,5-dioctyloxy-7,9-bis(2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketonewas described below:

1.2 g (5.4 mmol) of 1,3-bis(2-thiophene) acetone, 2.7 g (5.4 mmol) of2,7-dioctyloxy-4,5-diketone, and 40 mL of ethanol were successivelyadded to 250 mL of a single flask, and then heated for refluxing. Asmall amount of potassium hydroxide was dissolved in 2 mL of ethanol;then added to the reaction flask dropwise via a syringe. When thereaction solution turned dark green, the reaction was performed foradditional 10 minutes and then stopped; the reaction solution was pouredinto an ice-water bath. The reaction solution was filtrated, and washedwith ethanol, hot n-hexane for several times, and dried to obtain asolid product. In an embodiment, the temperature of the n-hexane was thesame as the reaction temperature, or the difference between thetemperature of the n-hexane and the reaction temperature was 5° C.Alternatively, a molar ratio of the potassium hydroxide and the1,3-bis(2-thiophene) acetone was 5:1.

MALDI-TOF-MS (m/z): 679.0 (M⁺).

Step four, the preparation of2,5-dioctyloxy-7,9-bis(2-trimethyltin-5-thiophen)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

Under a nitrogen atmosphere, 6.79 g (10 mmol) of the2,5-dioctyloxy-7,9-bis(2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 120 mL of anhydrous THF werecooled to −78° C.; then 5 mL (12 mmol) of n-butyllithium in 2.5M hexanesolution was slowly added, after that, the reaction solution wasincubated at −78° C. for 2 hours; then 4.5 mL (15 mmol) of trimethyl tinchloride was added, the reaction solution naturally returned to roomtemperature after incubating for 0.5 hours, then the reaction wasperformed for additional 24 hours and stopped. 50 mL of hexane was addedfor dilution, then the reaction solution was slowly poured into icewater, an organic phase product was obtained by extraction, the organicphase product was washed with 5% NaHCO₃ and saturated NaCl solution,respectively, then dried with anhydrous magnesium sulfate, filtrated,evaporated, and distilled under reduced pressure, excess trimethyl tinchloride was distilled out and a product was obtained.

MALDI-TOF-MS (m/z): 1004.6 (M⁺).

Step five, the preparation of benzodithiophene based copolymercontaining thieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.5 g (0.5 mmol) of2,5-dioctyloxy-7,9-bis(2-trimethyltin-5-thiophen)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.28 g (0.5 mmol) of4,6-dibromo-2-(1-(2-pentyl dodecanone)) thieno[3,4-b]thiophene(corresponding to the structural formula in the above equation,hereinafter similarly) were added to a reaction flask containing 10 mLof dry toluene, the reaction mixture was stirred under a stream ofnitrogen for 15 minutes, and a catalyst of Pd₂(dba)₃ and P(o-Tol)₃ wasadded rapidly to the reaction flask; wherein Pd₂(dba)₃ was 23 mg (0.025mmol, 5% mol); P(o-Tol)₃ was 152 mg (0.5 mmol); a molar ratio ofPd₂(dba)₃ and P(o-Tol)₃ was 1:20.

After the reaction mixture was stirred under a stream of nitrogen for 15minutes, the reaction mixture was heated to 80° C. for refluxing, andthe reaction solution was stirred for 72 hours then the reaction wasstopped, after the reaction solution was cooled to room temperature, thereaction solution was dried to about 5 mL via reduced pressuredistillation, then dropped into 300 mL of dry methanol, and continuouslystirred for about 4 hours, a solid was gradually precipitated, a solidpowder was obtained via suction filtration and dry. The solid powder wasdissolved with chloroform, purified by neutral alumina columnchromatography to remove the catalyst of Pd₂(dba)₃, the polymer solutionwas evaporated to about 5 mL, and the 5 mL solution was dropped into amethanol solvent and stirred for several hours, finally a polymer wascollected and dried, the polymer was extracted with Soxhlet extractor,thus the monodispersity of the polymer molecular weight was improved.

The molecular weight was tested via Gel Permeation Chromatography (GPC).GPC: Mn=64920, Polydispersity coefficient index (PDI)=1.5.

Example 2

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ is hexyl, R₂ is H, R₃ is 2-methyl thienyl; R₄ is H, R₅ isoctyl, n=55.

The preparation of the benzodithiophene based copolymer containingthieno [3,4-b]thiophene units includes the steps of:

Step one, the preparation of bis(4-dihexyl-2-thiophene) acetone wasdescribed below.

First, 7.6 g of DCC and 1.23 g of DMAP were dissolved in 70 mL ofdichloromethane via anhydrous treatment to form a reaction solution;under a nitrogen atmosphere, 60 mL of dichloromethane solutioncontaining 7.6 g of 4-hexyl-2-thiophene acetic acid was added to thereaction solution, the reaction was performed overnight. After thereaction was finished, the reaction solution was filtered,recrystallized with n-hexane for twice, and purified by columnchromatography to obtain a product.

MALDI-TOF-MS (m/z): 391 (M⁺)

Step two, the preparation of2,7-bis(2-methyl-5-thiophen)benzo[1,2-b:4,3-b′]dithiophene-4,5-diketonewas described below:

21.5 g (60 mmol) of 4,4′-bis(2-methyl-5-thiophen)thiophene was added to350 mL of dry 1,2-dichloroethane, then 3 mL (34.5 mmol) of oxalylchloride was added to the reaction flask for three times within 5 days,and the refluxing reaction was performed under an argon atmosphere for15 days. After the reaction was finished, the reaction solution wascooled to room temperature; and frozen overnight in the refrigerator;then filtered to obtain a red solid; then the red solid was washed withn-hexane and ethanol successively to obtain a product.

MALDI-TOF-MS (m/z): 413.0 (M⁺).

Step three, the preparation of2,5-bis(2-methyl-5-thiophen)-7,9-bis(4-hexyl-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

2.1 g (5.4 mmol) of bis(4-hexyl-2-thiophene) acetone, 2.2 g (5.4 mmol)of2,7-bis(2-methyl-5-thiophen)benzo[1,2-b:4,3-b′]dithiophene-4,5-diketone,and 60 mL of ethanol were successively added to 250 mL of single flask,and then heated for refluxing. A small amount of potassium hydroxide wasdissolved in 2 mL of ethanol; then added to the reaction flask dropwisevia a syringe. When the reaction solution turned dark green, thereaction was performed for additional 10 minutes and then stopped; thereaction solution was poured into an ice-water bath, then the reactionsolution was filtrated, and washed with ethanol, hot n-hexane forseveral times, and dried to obtain a solid product.

MALDI-TOF-MS (m/z): 765.0 (M⁺).

Step four, the preparation of2,5-bis(2-methyl-5-thiophen)-7,9-bis(4-hexyl-2-trimethyltin-5-thiophen)-81H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

Under a nitrogen atmosphere, 7.65 g (10 mmol) of the2,5-bis(2-methyl-5-thiophen)-7,9-bis(4-hexyl-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 150 mL of anhydrous THF werecooled to −78° C. 5 mL (12 mmol) of n-butyllithium of hexane solution(2.5M) was slowly added, after that, the reaction solution was incubatedat −78° C. for 2 hours; then 4.5 mL (15 mmol) of trimethyl tin chloridewas added, the reaction solution was naturally recovered to roomtemperature after incubating for 0.5 hours, the reaction was performedfor additional 24 hours and then stopped. 50 mL of hexane was added fordilution, then the reaction solution was slowly poured into ice water,an organic phase product was obtained by extraction, the organic phaseproduct was washed with 5% NaHCO₃ and saturated NaCl solution,respectively, then dried with anhydrous magnesium sulfate, filtrated,evaporated, and distilled under reduced pressure, excess trimethyl tinchloride was distilled out and a product was obtained.

MALDI-TOF-MS (m/z): 1093 (M⁺).

Step five, the preparation of benzodithiophene based copolymercontaining thieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.82 g (0.75 mmol) of2,5-bis(2-methyl-5-thiophen)-7,9-bis(4-hexyl-2-trimethyltin-5-thiophen)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.22 g (0.5 mmol) of4,6-dibromo-2-(1-octanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry tetrahydrofuran, i.e. a reactionflask containing 10 mL of dry tetrahydrofuran or a reaction flaskcontaining 10 mL of tetrahydrofuran via dry treatment, the reactionmixture was stirred under a stream of nitrogen for 15 minutes, and acatalyst of 14 mg (0.015 mmol, 3% mol) of Pd₂(dba)₃ and 68 mg (0.225mmol) of P(o-Tol)₃ was added rapidly to the reaction flask; wherein amolar ratio of Pd₂(dba)₃ and P(o-Tol)₃ was 1:15. After the reactionmixture was stirred under a stream of nitrogen for 15 minutes, thereaction mixture was heated to 60° C. for refluxing, and stirred for 60hours then the reaction was stopped, after the reaction solution wascooled to room temperature, the reaction solution was dried to about 5mL via reduced pressure distillation, then dropped into 300 mL of drymethanol, and continuously stirred for about 4 hours, a solid wasgradually precipitated, a solid powder was obtained via suctionfiltration and dry. The solid powder was dissolved with chloroform,purified by neutral alumina column chromatography to remove the catalystof Pd₂(dba)₃, the polymer solution was evaporated to about 5 mL, and the5 mL solution was dropped into a methanol solvent and stirred forseveral hours, finally a polymer was collected and dried, the polymerwas extracted with Soxhlet extractor, thus the monodispersity of thepolymer molecular weight was improved.

GPC: Mn=57420, PDI=1.8.

Example 3

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ is 16 alkyl, R₂ is H, R₃ is methoxyl; R₄ is H, R₅ is methyl,n=35.

Step one, the preparation of2,5-dimethoxybenzene-7,9-bis(4-hexadecyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 1241 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.74 g (0.6 mmol) of2,5-dimethoxybenzene-7,9-bis(4-hexadecyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.17 g (0.5 mmol) of4,6-dibromo-2-(ethane-1-ketone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry DMF, the reaction mixture wasstirred under a stream of nitrogen for 15 minutes, and a catalyst ofPd₂(dba)₃ and P(o-Tol)₃ was added rapidly to the reaction flask; whereinthe Pd₂(dba)₃ was 0.046 mg (0.00005 mmol, 0.01% mol), the P(o-Tol)₃ was0.0304 mg (0.0001 mmol), a molar ratio of Pd₂(dba)₃ and P(o-Tol)₃ was1:2. After the reaction mixture was stirred under a stream of nitrogenfor 15 minutes, the reaction mixture was heated to 120° C. forrefluxing, and stirred for 48 hours then the reaction was stopped, afterthe reaction solution was cooled to room temperature, the reactionsolution was dried to about 5 mL via reduced pressure distillation, thendropped into 300 mL of dry methanol and continuously stirred for about 4hours, a solid was gradually precipitated, a solid powder was obtainedvia suction filtration and dry. The solid powder was dissolved withchloroform, purified by neutral alumina column chromatography to removethe catalyst of Pd₂(dba)₃, the polymer solution was evaporated to about5 mL, then the 5 mL solution was dropped into a methanol solvent andstirred for several hours, finally a polymer was collected and dried,the polymer was extracted with Soxhlet extractor, thus themonodispersity of the polymer molecular weight was improved.

GPC: Mn=38290, PDI=1.8.

Example 4

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ is H, R₂ is methyl, R₃ is 16 alkoxy; R₄ is H, R₅ is butyl,n=30.

Step one, the preparation of2,5-di(hexadecyloxy)-7,9-bis(3-methyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 1241 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.62 g (0.5 mmol) of2,5-di(hexadecyloxy)-7,9-bis(3-methyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.19 g (0.5 mmol) of4,6-dibromo-2-(1-pentanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry DMF, the reaction mixture wasstirred under a stream of nitrogen for 15 minutes, and a catalyst of0.046 mg (0.00005 mmol, 0.01% mol) of Pd₂(dba)₃ and 0.0304 mg (0.0001mmol) of P(o-Tol)₃ was added rapidly to the reaction flask; wherein amolar ratio of Pd₂(dba)₃ and P(o-Tol)₃ was 1:2. After the reactionmixture was stirred under a stream of nitrogen for 15 minutes, thereaction mixture was heated to 120° C. for refluxing, and stirred for 48hours then the reaction was stopped, after the reaction solution wascooled to room temperature, the reaction solution was dried to about 5mL via reduced pressure distillation, then dropped into 300 mL of drymethanol, and continuously stirred for about 4 hours, a solid wasgradually precipitated, a solid powder was obtained via suctionfiltration and dry. The solid powder was dissolved with chloroform,purified by neutral alumina column chromatography to remove the catalystof Pd₂(dba)₃, the polymer solution was evaporated to about 5 mL, thenthe 5 mL solution was dropped into a methanol solvent and stirred forseveral hours, finally a polymer was collected and dried, the polymerwas extracted with Soxhlet extractor, thus the monodispersity of thepolymer molecular weight was improved.

GPC: Mn=34080, PDI=1.8.

Example 5

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ and R₂ are identical methyl, R₃ is 16 alkoxy; R₄ is H, R₅ isbutyl, n=20.

Step one, the preparation of2,5-di(hexadecyl)-7,9-bis(3,4-dimethyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 1237 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.62 g (0.5 mmol) of2,5-di(hexadecyloxy)-7,9-bis(3,4-dimethyl-5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.19 g (0.5 mmol) of4,6-dibromo-2-(1-pentanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry benzene, the reaction mixture wasstirred under a stream of nitrogen for 15 minutes, and a catalyst of28.9 mg (0.025 mmol, 0.5% mol) of tetrakis(triphenylphosphine)palladiumwas added rapidly to the reaction flask. After the reaction mixture wasstirred under a stream of nitrogen for 15 minutes, the reaction mixturewas heated to 80° C. for refluxing, and stirred for 24 hours then thereaction was stopped, after the reaction solution was cooled to roomtemperature, the reaction solution was dried to about 5 mL via reducedpressure distillation, then dropped into 300 mL of dry methanol, andcontinuously stirred for about 4 hours, a solid was graduallyprecipitated, a solid powder was obtained via suction filtration anddry. The solid powder was dissolved with chloroform, purified by neutralalumina column chromatography to remove the catalyst oftetrakis(triphenylphosphine)palladium, the polymer solution wasevaporated to about 5 mL, and the 5 mL solution was dropped into amethanol solvent and stirred for several hours, finally a polymer wascollected and dried, the polymer was extracted with Soxhlet extractor,thus the monodispersity of the polymer molecular weight was improved.

GPC: Mn=22640, PDI=2.2.

Example 6

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ and R₂ are identical H, R₃ is hexyl; R₄ is H, R₅ is butyl,n=15.

Step one, the preparation of2,5-dihexyl-7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 900 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.45 g (0.5 mmol) of2,5-dihexyl-7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.19 g (0.5 mmol) of4,6-dibromo-2-(1-pentanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry methylbenzene, the reactionmixture was stirred under a stream of nitrogen for 15 minutes, and acatalyst of 3.5 mg (0.005 mmol, 1% mol) of Pd(PPh₃)₂Cl₂ was addedrapidly to the reaction flask. After the reaction mixture was stirredunder a stream of nitrogen for 15 minutes, the reaction mixture washeated to 110° C. for refluxing, and stirred for 24 hours then thereaction was stopped, after the reaction solution was cooled to roomtemperature, the reaction solution was dried to about 5 mL via reducedpressure distillation, then dropped into 300 mL of dry methanol, andcontinuously stirred for about 4 hours, a solid was graduallyprecipitated, a solid powder was obtained via suction filtration anddry. The solid powder was dissolved with chloroform, purified by neutralalumina column chromatography to remove the catalyst of Pd(PPh₃)₂Cl₂,the polymer solution was evaporated to about 5 mL, and the 5 mL solutionwas dropped into a methanol solvent and stirred for several hours,finally a polymer was collected and dried, the polymer was extractedwith Soxhlet extractor, thus the monodispersity of the polymer molecularweight was improved.

GPC: Mn=11925, PDI=2.2.

Example 7

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ and R₂ are identical H, R₃ is methyl; R₄ is H, R₅ is butyl,n=10.

Step one, the preparation of2,5-dimethyl-7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8 ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 760 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.38 g (0.5 mmol) of2,5-dimethyl-7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.19 g (0.5 mmol) of4,6-dibromo-2-(1-pentanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry methylbenzene, the reactionmixture was stirred under a stream of nitrogen for 15 minutes, and acatalyst of 11.6 mg (0.01 mmol, 2% mol) oftetrakis(triphenylphosphine)palladium was added rapidly to the reactionflask. After the reaction mixture was stirred under a stream of nitrogenfor 15 minutes, the reaction mixture was heated to 110° C. forrefluxing, and stirred for 24 hours then the reaction was stopped, afterthe reaction solution was cooled to room temperature, the reactionsolution was dried to about 5 mL via reduced pressure distillation, thendropped into 300 mL of dry methanol, and continuously stirred for about4 hours, a solid was gradually precipitated, a solid powder was obtainedvia suction filtration and dry. The solid powder was dissolved withchloroform, purified by neutral alumina column chromatography to removethe catalyst of tetrakis(triphenylphosphine)palladium, the polymersolution was evaporated to about 5 mL, and the 5 mL solution was droppedinto a methanol solvent and stirred for several hours, finally a polymerwas collected and dried, the polymer was extracted with Soxhletextractor, thus the monodispersity of the polymer molecular weight wasimproved.

GPC: Mn=6550, PDI=2.2.

Example 8

A benzodithiophene based copolymer containing thieno[3,4-b]thiopheneunits having a following structural formula is provided:

wherein R₁ and R₂ are identical H, R₃ and R₄ are identical H, R₅ isbutyl, n=8.

Step one, the preparation of7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone was described below:

The synthesis method was referred to the steps one to four of Example 1.

MALDI-TOF-MS (m/z): 732 (M⁺).

Step two, the preparation of benzodithiophene based copolymer containingthieno[3,4-b]thiophene units was described below:

Under a nitrogen atmosphere, 0.37 g (0.5 mmol) of7,9-bis(5-trimethyltin-2-thiophene)-8H-cyclopentadienebenzo[1,2-b:4,3-b′]dithiophene-8-ketone and 0.19 g (0.5 mmol) of4,6-dibromo-2-(1-pentanone) thieno[3,4-b]thiophene were added to areaction flask containing 10 mL of dry benzene, the reaction mixture wasstirred under a stream of nitrogen for 15 minutes, and a catalyst of0.29 mg (0.00025 mmol, 0.05% mol) oftetrakis(triphenylphosphine)palladium was added rapidly to the reactionflask. After the reaction mixture was stirred under a stream of nitrogenfor 15 minutes, the reaction mixture was heated to 80° C. for refluxing,and stirred for 12 hours then the reaction was stopped, after thereaction solution was cooled to room temperature, the reaction solutionwas dried to about 5 mL via reduced pressure distillation, then droppedinto 300 mL of dry methanol, and continuously stirred for about 4 hours,a solid was gradually precipitated, a solid powder was obtained viasuction filtration and dry. The solid powder was dissolved withchloroform, purified by neutral alumina column chromatography to removethe catalyst of tetrakis(triphenylphosphine)palladium, the polymersolution was evaporated to about 5 mL, and the 5 mL solution was droppedinto a methanol solvent and stirred for several hours, finally a polymerwas collected and dried, the polymer was extracted with Soxhletextractor, thus the monodispersity of the polymer molecular weight wasimproved.

GPC: Mn=5016, PDI=2.3.

The present invention also provides uses of benzodithiophene basedcopolymer containing thieno[3,4-b]thiophene units according to any ofthe above embodiment in polymer solar cell, polymer organicelectroluminescent devices, polymer organic field effect transistors,polymer organic optical storage, polymer organic non-linear devices, orpolymer organic laser. Several specific examples are given as follow.

Example 9

An organic solar cell device is provided using the copolymer of Example1, i.e. the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units is used as an active layer material, thestructure of the organic solar cell device is shown in FIG. 1.

Preparation of the organic solar cell device: the structure of thedevice was: glass/ITO/PEDOT:PSS/active layer/Al, wherein the ITO (indiumtin oxide) was the indium tin oxide with a sheet resistance of 10 to 20Ω/sq, PEDOT was poly(3,4-ethylenedioxythiophene), PSS was poly(styrenesulfonic acid); ITO glass was cleaned by ultrasonic, treated with anoxygen-Plasma, and then the ITO glass was spin-coated with PEDOT:PSS.The copolymer of Example 1 was used as electron donor material and PCBMwas used as the electron acceptor material, which was coated byspin-coating, the metal aluminum electrode was prepared by vacuumdeposition techniques, the organic solar cell device was thus obtained.

Example 10

An organic electroluminescent device is provided using the copolymer ofExample 2, i.e. the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units is used as an active layer material, thestructure of the organic electroluminescent device is shown in FIG. 2.

Preparation of the organic electroluminescent device: the structure ofthe device was: ITO/copolymers of the present invention/LiF/Al, anindium tin oxide (ITO) with a sheet resistance of 10 to 20 Ω/sq wasdeposited on a glass to form a transparent anode, a layer of thecopolymer of Example 2 was prepared on the ITO by spin-coating to form aluminescent layer, LiF was deposited on the luminescent layer byevaporation to form a buffer layer, finally, the metal Al was depositedon the buffer layer by vacuum evaporation to form the cathode of thedevice.

Example 11

An organic field effect transistor is provided using the copolymer ofExample 3, i.e. the benzodithiophene based copolymer containingthieno[3,4-b]thiophene units is used as an organic semiconductormaterial, the structure of the organic field effect transistor is shownin FIG. 3.

Preparation of the organic field effect transistors: a heavily dopedsilicon (Si) wafer was used as substrate, an SiO₂ layer with a thick of450 nm was used as an insulating layer, a source electrode (S) and adrain electrode (D) were made of gold, the copolymers of Example 3 wasan organic semiconductor layer, which was spin-coated onto the SiO₂layer modified with octadecyltrichlorosilane (OTS).

Applicant believes that, according to this description, those skilled inthe art are sufficient to understand how to implement the invention, andassess the context defined by the claims may be implemented with theeffect, those skilled in the art can determine and prove thebenzodithiophene based copolymer containing thieno[3,4-b]thiophene unitsmay be applied in the uses.

It should be understood that the preferred specific embodiments arespecific and detailed, and should not be interpreted as limitations tothe scope of the invention, as defined by the appended claims.

What is claimed is:
 1. A benzodithiophene based copolymer containingthieno[3,4-b] thiophene units, having a structural formula:

wherein R₁ and R₂ are selected from the group consisting of H, and C₁ toC₁₆ alkyl, respectively; R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, and thienylsubstituted by C₁ to C₁₆ alkyl, respectively; R₅ is C₁ to C₁₆ alkyl; nis a natural number from 7 to
 80. 2. The benzodithiophene basedcopolymer according to claim 1, wherein the alkyl is a linear alkyl orbranched alkyl; the alkoxy is a linear alkoxy or branched alkoxy.
 3. Thebenzodithiophene based copolymer according to claim 2, wherein n is anatural number from 8 to
 60. 4. The benzodithiophene based copolymeraccording to claim 3, wherein R₁ is the same as R₂, and/or R₃ is thesame as R₄.
 5. The benzodithiophene based copolymer according to claim3, wherein R₁, R₂, R₃, R₄ and R₅ are selected from a combination of: R₁and R₂ are H, R₃ and R₄ are methyl, R₅ is n-butyl; or R₁, R₂, R₃, and R₄are H, R₅ is methyl; or R₁ is ethyl, R₂ is pentyl, R₃ is H, R₄ is3-methyl thienyl, R₅ is 2-methyl butyl; or R₁ and R₂ are identicalpropyl, R₃ is 12 alkyl, R₄ is ethoxyl, R₅ is 2,4-dimethyl-3-ethylheptyl; or R₁ is butyl, R₂ is 12 alkyl, R₃ is 14 alkoxy, R₄ is octyl, R₅is 2,2,4-trimethyl pentyl; or R₁ and R₂ are identical H, R₃ is octoxy,R₄ is H, R₅ is 16 alkyl; or R₁ is hexyl, R₂ is H, R₃ is 2-methylthienyl, R₄ is H, R₅ is octyl; or R₁ is 16 alkyl, R₂ is H, R ismethoxyl, R₄ is H, R₅ is methyl; or R₁ is H, R₂ is methyl, R₃ is 16alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂ are identical methyl, R₃ is16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂ are identical H, R₃ ishexyl, R₄ is H, R₅ is butyl; or R₁ and R₂ are identical H, R₃ is methyl,R₄ is H, R₅ is butyl; or R₁ and R₂ are identical H, R₃ and R₄ areidentical H, R₅ is butyl.
 6. A method for preparing a benzodithiophenebased copolymer containing thieno[3,4-b]thiophene units, comprising thesteps of: adding M1 and M2 to a solvent in an oxygen-free environment;

performing a refluxing reaction in the presence of catalyst; thereaction formula is as follows:

wherein R₁ and R₂ are selected from the group consisting of H, and C₁ toC₁₆ alkyl, respectively; R₃ and R₄ are selected from the groupconsisting of H, C₁ to C₁₆ alkyl, C₁ to C₁₆ alkoxy, and thienylsubstituted by C₁ to C₁₆ alkyl, respectively; R₅ is C₁ to C₁₆ alkyl; nis a natural number from 7 to 80; a molar ratio between M1 and M2 is 1:1to 1.5:1; the solvent is at least one selected from the group consistingof toluene, tetrahydrofuran, benzene, and N,N-dimethylformamide; thecatalyst is organic palladium or a mixture of organic palladium andorganic phosphine ligand, a molar amount of the catalyst is 0.01% to 5%of the molar amount of the M2; the organic palladium is Pd₂(dba)₃,Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂, a molar ratio between the organic palladiumand the organic phosphine ligand in the mixture is 1:2 to 1:20; theorganic phosphine ligand is P(o-Tol)₃ or tricyclohexylphosphine; thereaction is performed at a temperature ranging from 60° C. to 120° C.for 12 to 72 hours.
 7. The method according to claim 6, wherein M1 issynthesized by the steps of: S1, dissolving a compound A with a properamount of dichloromethane to form a solution, under a nitrogenatmosphere, adding the solution dropwise to anhydrous dichloromethanecontaining 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine by asyringe; a molar ratio of the compound A, the1,3-dicyclohexylcarbodiimide, and the 4-dimethylaminopyridine is 3:3:1,the reaction is performed for 8 to 24 hours to obtain a compound B, thereaction formula is as follows:

S2, adding the compound B and the compound C to a solvent according amolar ratio of 1:1, the solvent is ethanol or propanol; heating to 78°C. to 100° C. to perform a refluxing reaction, then adding a reducingagent, and reacting for additional 10 minutes to obtain a compound D,wherein the reducing agent is potassium hydroxide or sodium hydroxide, amolar ratio between the reducing agent and the compound B is 5:1;

S3, under a nitrogen atmosphere, dissolving the compound D to anhydroustetrahydrofuran and cooling to −78° C.; adding an n-hexane solutioncontaining n-butyllithium slowly, a molar ratio between then-butyllithium and the compound D is 1:2.5; reacting under stirring at atemperature of −78° C. for 2 hours; then adding trimethyl tin chloride,a molar ratio between the trimethyl tin chloride and the compound D is2.5:1; incubating for 0.5 hours and then returning to room temperature;and reacting for additional 24 hours to obtain the compound M1; thereaction formula is as follows:


8. The method according to claim 7, wherein the alkyl is a linear alkylor branched alkyl; the alkoxy is a linear alkoxy or branched alkoxy, andn is a natural number from 8 to
 60. 9. The method according to claim 8,wherein R₁ is the same as R₂, and/or R₃ is the same as R₄; or R₁, R₂,R₃, R₄ and R₅ are selected from a combination of: R₁ and R₂ are H, R₃and R₄ are methyl, R₅ is n-butyl; or R₁, R₂, R₃, and R₄ are H, R₅ ismethyl; or R₁ is ethyl, R₂ is pentyl, R₃ is H, R₄ is 3-methyl thienyl,R₅ is 2-methyl butyl; or R₁ and R₂ are identical propyl, R₃ is 12 alkyl,R₄ is ethoxyl, R₅ is 2,4-dimethyl-3-ethyl heptyl; or R₁ is butyl, R₂ is12 alkyl, R₃ is 14 alkoxy, R₄ is octyl, R₅ is 2,2,4-trimethyl pentyl; orR₁ and R₃ are identical H, R₃ is octoxy, R₄ is H, R₅ is 16 alkyl; or R₁is hexyl, R₂ is H, R₃ is 2-methyl thienyl, R₄ is H, R₅ is octyl; or R₁is 16 alkyl, R₂ is H, R₃ is methoxyl, R₄ is H, R₅ is methyl; or R₁ is H,R₂ is methyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical methyl, R₃ is 16 alkoxy, R₄ is H, R₅ is butyl; or R₁ and R₂are identical H, R₃ is hexyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ is methyl, R₄ is H, R₅ is butyl; or R₁ and R₂ areidentical H, R₃ and R₄ are identical H, R₅ is butyl.
 10. Thebenzodithiophene based copolymer containing thieno[3,4-b]thiophene unitsaccording to claim 1 for use as a component part of polymer solar cells,polymer organic electroluminescent devices, polymer organic field effecttransistors, polymer organic optical storage, polymer organic nonlineardevices, or polymer organic laser.